Understanding CTCSS and DCS

This video explains the basic technical principles behind CTCSS (continuous tone coded squelch system) and DCS (digitally coded squelch) as well as how they are used in analog radio systems.

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Index
00:15 About squelch
1:45 User squelch and talk groups
2:10 Squelch and repeaters
3:35 CTCSS (continuous tone coded squelch system)
4:21 CTCSS tones
4:57 DCS (digitally coded squelch)
5:42 DCS codeword example
6:03 Standard DCS codes
6:48 Polarity inversion
7:20 Turn off code
8:10 Summary

[stephenmitchell]

👍 Thank you so much for posting this. This just connected the dots and now I'm receiving lima charlie!

[judeogbonna]

Super clear simple and straight. Thanks

[davidhartinger]

Nice work. Makes CTCSS and DCS more easily understood.

[gregdomingo]

Wow thanks! This is crystal clear explanation.

[jaybarr]

Very good, clear explanation. Thank you!

[wisteela]

Very informative. Great explanation of how DCS works.

[violtailer]

4:55 not low pass, but high pass filter is used to remove frequencies belof some f0

[andreiamg]

Squelch filter - I believe it is a high pass filter to remove the <300 Hz components rather than low pass as stated.

[pablo_fernandez]

Thank you for the clarity in this video.

[حضرمون]

Thanks for simplifying. I have learned a thing or two from this video. 🙏🙏

[philhamlin]

Nicely done. Ready helped my understanding.

[alnofaly]

I work in an isolated place in the Middle East, where I use the Alinco DR-B185 that has a DCS feature, where I only pick up a full signal for my colleagues without being able to hear them talking! Is there any clarification on that please?

[srviejo]

With all due respect, this video is in error at time stamp 4:50, where the narration indicates that a low pass filter routes audio to the speaker. This would result in only the CTCSS tones being rendered at the speaker. In practice, a low pass filter routes audio from the discriminator to the tone decoder, but a band pass (often 300 Hz to 3, 000 Hz) routes audio to the speaker, and a high-pass filter (above the band-pass filter frequency range) routes audio to the noise gate for non CTCSS/DCS squelch behavior.

[drakeblackk]

Well, i never really got into dcs and stuff, i just got a better radio (Yaesu 7800E) and i was thinking about if there is any code that can be used to communicate in private, without people hearing it without these turned on?
Like when i test with my UVK5 and Yaesu, so noone can hear that only between the handheld and the Yaesu

[gianluigiredolfini]

Super clear thanks for a job well done!

[richiec]

Great, easy to understand explanation of these tones. I have a question: In some radios they state that there are “privacy tones” or “sub-channels”. I believe that these are are either CTCSS or DCS tones but there is no mention of them in the accompanying literature. Am I correct?

[ErrorMargin]

Assuming simplex (not using a repeater) radio to radio transmission, how do noise squelch and user squelch interact? Does the signal have to break noise squelch before the radio will check for the tone or code to see if user squelch should be opened? Or is it the other way around? Would it make sense to turn off noise squelch when using user squelch so that if the signal is strong enough for the radio to detect the user squelch tone or code then squelch is opened regardless of signal strength or noise?

[Nab-Asn]

Thank you so much for this great vedio

[richpaul]

Excellent explanation! Now, I need to try and put it into a real-world application. The first thing I think I would want to do is to scan for any CTCSS or DCS users, no? I mean, I don't really need to speak to a user, (at least, not at first), but I only want to confirm that my SR 955HPC V2 is able to receive from someone using that system.

I've got a long way to go before I plan to attempt transmitting to a CTCSS/DCS user. For now, I'd be happy just confirming that I have found and am receiving a transmission from a CTCSS or DCS user.
Thanks for the video!
Rich

[mattvikich]

Awesome vid. Can two radios on the same dcs channel be used threw a repeater on duplex? Im guessing everone would hear the "tail" of the repeater which could get annoying for them?